Noncovalent interaction of cyanidin-3-O-glucoside with whey protein isolate and β-lactoglobulin: Focus on fluorescence quenching and antioxidant properties

Cyanidin-3-O-glucoside (C3G) is the major anthocyanin which has a variety of biological activities. Whey protein isolate (WPI) is an essential protein of milk with β-lactoglobulin (β-LG) as the most abundant component. In this study, noncovalent interactions of C3G with WPI and β-LG and antioxidant properties of their complexes were investigated. Analysis of the fluorescence data showed that C3G-induced quenching was not controlled by dynamic collision, instead is due to the formation of a complex, therefore the interactions between C3G and dairy proteins was typical static quenching. For the C3G-β-LG complex, the binding constant and number of binding sites were determined, and hydrophobic interactions played the major role. Three concentrations of C3G displayed a remarkable synergism of radical scavenging activity, reducing power and Fe2+ chelating capacity with both milk proteins. Conclusively, the study provided a theoretical base for applications of phytochemicals in the developments of healthier diet and nutraceutical.